1. Field of Invention
The invention relates generally to an apparatus for recuperation of hydraulic energy. More particularly, the invention relates to an apparatus for recuperation of hydraulic energy, typically from an actuator, typically a hoist, where a first drive of a first hydraulic machine and a second drive of a second hydraulic machine are mechanically connected, and where the first hydraulic machine is in hydraulic communication with an actuator. The invention also relates to a method for operation of the apparatus.
2. Background of the Technology
Hydraulic hoisting systems are included in an array of equipment such as offshore and land based drilling rigs, winches and equipment. The hoisting systems are regarded as the backbone of a rig in terms of handling a drill as well as controlling a drilling process.
Several of these hoisting systems exhibit a cyclic load profile where a load is repeatedly lifted and lowered. At least in some of the prior art hoisting systems potential energy is dissipated as heat during lowering of the load.
Such systems are characterized by a large variation in the operational envelope in terms of hook load and lifting speed, as well as duration of a particular operation. The hoisting system is thus dimensioned in order to fulfill the maximum power requirements given by a certain operation. Therefore, the hydraulic power unit of a typical hoisting system consists of several hydraulic machines.
It is known to recuperate at least some of such potential energy by utilization of a hydraulic transformer. U.S. Pat. No. 3,627,451 discloses a hydraulic transfer unit for transferring hydraulic power at the same pressures and in either direction between two separate and isolated hydraulic control systems.
U.S. Pat. No. 7,249,457 discloses a hydraulic system that has gravitational load energy recuperation by opening a recuperation piloted valve with a pilot pressure supplied by a hydraulic pump so as to drive a recuperation hydraulic motor with a source of fluid pressurized by gravity from the load. The recuperation hydraulic motor drives the mechanical drive train of a prime mover that drives the pump that supplies the load, and other pumps that supply other loads.
None of the prior art documents discloses an energy management system for cyclic load profiles in order to estimate the energy recuperation potential to a hoisting system where energy is stored in an accumulator.
The purpose of the invention is to overcome or reduce at least one of the disadvantages of the prior art.